leverage Plotly.react()

[cpsievert]

This change is kinda scary, but the speed improvement seems to be worth it. See, for example, https://github.com/ropensci/plotly/tree/master/inst/examples/shiny/Diamonds

UPDATE: this appears to break some crosstalk+shiny use cases, such as https://github.com/cpsievert/housing-data-challenge-plotly